1. Field of the Invention
The present general inventive concept relates to multimedia and radio electronics, and more particularly, to a method and apparatus used to perform digital signal processing to improve the quality of audio signals.
2. Description of the Related Art
Various methods and systems have been developed to improve the quality of audio signals to a degree noticeable by an audience by recovering various high-frequency component characteristics that may have been lost during encoding of the audio signals or during the transmission of the audio signals via channels with poor transmission capability.
One conventional method of recovering audio information lost from audio signals is disclosed in Russian Patent No. RU 2,194,361. In this patented method of recovering lost audio information, digital data is divided into a plurality of blocks of digits in which the digits are arranged in a descending order based on a significance of digit position, thus providing a sufficient level of accuracy to reconstruct a block structure.
In another conventional method of recovering audio information lost from audio signals, which is simpler than the method disclosed in Russian Patent No. RU 2,194,361, correction signals are generated by processing low-frequency components of audio signals. U.S. Pat. Nos. 6,335,973 and 6,023,513, for example, disclose this type of method, and particularly, a method of generating high-frequency harmonic components based on low-frequency components of audio signals. Nonlinear transformation is generally used for generating high-frequency harmonic components based on low-frequency components of audio signals.
In addition to the above conventional audio information recovery methods, U.S. Pat. No. 5,754,666 discloses a method of generating high-frequency components of an audio signal using a high-frequency noise generator. In this patented method, noise parameters are chosen through analysis of low-frequency components of audio signals.
Further, U.S. Pat. No. 5,893,068 relates to a method of expanding a range of frequencies of digital audio signals, thereby enabling addition of high-frequency components of the digital audio signals.
However, due to the characteristic of the human sense of hearing in which the higher the frequency of sound, the lower the frequency resolution of the human ears, it is difficult to improve the quality of audio signals to a degree perceivable by an audience, and which is the same quality as corresponding original audio signals, simply by expanding the frequency range of the audio signals or shifting the frequency spectrum of the audio signals.